PRO-BOOST-LC: Whole-Gland Boost Strategies Versus SBRT Monotherapy in PSMA-Staged Localized and Locally Advanced Prostate Cancer

PRO-BOOST-LC is a prospective, multicenter, randomized clinical trial designed for patients with localized prostate cancer who do not have evidence of lymph node or distant metastases based on modern PSMA PET imaging. Prostate cancer is one of the most common cancers in men. For patients with disease confined to the prostate, radiotherapy is a well-established and effective curative treatment option. Over the past decades, research has shown that delivering higher radiation doses to the prostate can improve cancer control and reduce the risk of disease recurrence. However, higher radiation doses may also increase the risk of side effects affecting urinary, bowel, and sexual function. For this reason, different radiation techniques have been developed to safely deliver higher doses while protecting surrounding healthy organs. Several approaches to radiation dose escalation are currently used in clinical practice. These include stereotactic body radiotherapy (SBRT), which delivers radiation in a small number of highly precise treatments, as well as brachytherapy, where radioactive sources are placed directly inside the prostate for a short time (high-dose-rate brachytherapy) or permanently (low-dose-rate brachytherapy). Although all these approaches are accepted and widely used, it is not known which strategy provides the best balance between cancer control, treatment-related side effects, and long-term quality of life, particularly when modern imaging techniques are used to accurately stage the disease. The PRO-BOOST-LC study aims to directly compare different radiation dose escalation strategies using a standardized treatment framework. All participants enrolled in the study will have localized prostate cancer staged with PSMA PET imaging to exclude metastatic disease. Participants will then be randomly assigned to one of four treatment groups. One group will receive SBRT alone to the prostate. The other three groups will receive a short course of external beam radiotherapy followed by an additional focused radiation boost delivered using one of three methods: high-dose-rate brachytherapy, low-dose-rate brachytherapy, or SBRT. All treatment approaches used in this study are established methods routinely applied in clinical practice. Randomization ensures that each participant has an equal chance of being assigned to any of the treatment groups. This allows the study to fairly compare outcomes between the different strategies. The main objective of the trial is to determine whether adding a radiation boost improves treatment outcomes compared with SBRT alone. The primary outcome measure is failure-free survival, which includes cancer recurrence, disease progression, the need for additional cancer treatment, or death from any cause. Secondary outcomes include the development of distant metastases, overall survival, treatment-related side effects, and patient-reported quality of life. Participants will be closely monitored throughout the study. Before treatment, patients will undergo clinical evaluation, blood tests including prostate-specific antigen (PSA), imaging studies, and quality-of-life assessments. During and after treatment, participants will attend regular follow-up visits. These visits will include clinical examinations, PSA testing, assessment of treatment-related side effects, and completion of standardized questionnaires evaluating urinary, bowel, and sexual function, as well as overall quality of life. Imaging studies, including PSMA PET scans, will be performed when clinically indicated to assess for possible disease recurrence or progression. The study is designed to follow participants for many years in order to capture both early and long-term outcomes. By using modern radiotherapy techniques, standardized treatment protocols, and comprehensive follow-up, PRO-BOOST-LC aims to generate high-quality evidence that will help guide future treatment decisions for patients with localized prostate cancer. The results of this trial are expected to improve understanding of how best to use radiation dose escalation to maximize cancer control while minimizing side effects and preserving quality of life in the era of advanced imaging and precision radiotherapy. Participation in this study does not involve experimental or unproven treatments. All radiation techniques used in PRO-BOOST-LC are approved, widely available, and considered standard of care in many treatment centers worldwide. The study focuses on optimizing how these existing techniques are combined and delivered, rather than introducing new drugs or devices. Participation may involve additional follow-up assessments and questionnaires compared with routine care, but treatment decisions are made within established clinical practice guidelines. Patients may or may not directly benefit from participation, but the information gained from this study may help improve future treatment strategies for men with localized prostate cancer.